(CNN) - The Transportation Security Agency has issued an advisory about the Muslim holy month of Ramadan, telling its workforce and passengers that they may observe Muslims fasting, carrying prayer beads and whispering prayers on planes and in airports.

Ramadan begins this week, though the exact date varies depending on locale. It is the holiest month of the year for the world's 1.5 billion Muslims, during which many fast during daylight hours and dedicate more time than usual to praying and reading the Quran.

"Whenever the TSA is trying to create an environment of understanding, we welcome that," said Haris Tarin, director of the Muslim Public Affairs Council's Washington office. "At the same time, it highlights certain actions that can make the American Muslim population seem almost alien."

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